JPH09185080A - Liquid crystal electro-optical device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the ununiformity of electric lines of force in a cell thickness direction and to obtain a fine display characteristic in a liquid crystal electro-optical device for driving a liquid crystal material by impressing electric fields parallel with substrates. SOLUTION: In the liquid crystal electro-optical device holding the liquid crystal material between a pair of translucent substrates 101, 102, switching elements, liquid crystal material driving drain electrodes 115, common electrodes 107, and gate electrodes 105 are formed on one substrate 101, and an electric field parallel with the substrate 101 is impressed between the drain electrode 115 and the common electrode 107. On the other hand, the switching elements and the electrodes such as drain electrodes 116, common electrodes 108, etc., are formed also on the other substrate 102 and the liquid crystal material is driven by forming electric fields parallel with the substrates 101, 102 between electrodes on the substrates 101, 102. The electric field formed between the electrodes 115, 107 is smoothed by the electric field formed between the electrodes 116, 108.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal electro-optical device having good electric characteristics and viewing angle characteristics and capable of obtaining a uniform display on the entire screen.

[0002]

2. Description of the Related Art As a method for widening the viewing angle of a liquid crystal electro-optical device, a method in which the direction of an electric field applied to liquid crystal is made substantially parallel to a substrate surface (hereinafter referred to as a super TFT method)
Is disclosed, for example, in Japanese Patent Laid-Open No. 6-160878. In this case, the source electrode formed on one substrate,
An electric field is induced between the common electrodes, and liquid crystal molecules are aligned in the direction of the electric field. Further, in Japanese Patent Laid-Open No. 6-214244, the electric field applied to the liquid crystal is made uniform by making the electrodes have a high cell thickness.

In such an electro-optical device, since switching is performed while maintaining the long axis of the liquid crystal molecule parallel to the substrate, there is little change in the optical characteristics of the liquid crystal depending on the viewing angle. For this reason, light leakage due to a viewing angle, reduction in contrast, and the like are smaller than those in the conventional TN and STN systems.

[0004]

However, the conventional super TFT type electrode arrangement is formed only on one of the pair of substrates, and an electric field is easily applied to the region close to the electrodes. However, there is a problem in that the electric field strength decreases in the region directly above the electrodes, and therefore the switching of the liquid crystal material varies within the cell.

This is a drawback which is particularly noticeable in the super TFT system in which the liquid crystal is driven by utilizing the lateral electric field.

The variation of the electric field will be described with reference to FIG. Here, for simplicity, a pair of substrates (3
01) and (303) are arranged so as to be superposed at a constant interval, and a plurality of parallel electrodes (302), (305) formed on one substrate (301) and having a trapezoidal cross section and a constant electrode interval. ) Between positive, negative, positive,
A mode of the lines of electric force (304) around the electrodes when voltages having different polarities such as negative and ... Are applied alternately will be described. (For the electric lines of force formed by electric charges, refer to books on electromagnetics, such as "Electromagnetics" by Kazuyoshi Nagata, Asakura Shoten, and "Goto-Yamazaki Co-ed." Detailed Electromagnetics Exercises ", Kyoritsu Publishing.)

One electrode (302) on the substrate (301)
Electric lines of force (304) emitted from the substrate (303)
The other electrode (305)
However, as can be seen from FIG. 3, the electric flux density (proportional to the number of lines of electric force per unit area) differs in the vicinity of the substrate surface where the electrodes are formed and in the vicinity of the other substrate surface.

Although an electric field between electrodes having a trapezoidal cross section is shown here as an example, the same applies to electrodes having other shapes such as a rectangular cross section. This is because the electric field is formed perpendicularly to the electrode surface, and the distribution of the lines of electric force becomes non-uniform in the vicinity of the electrode and in other portions.

The lines of electric force represent the direction of the electric field at each place. The liquid crystal material changes its orientation state by the interaction with the electric field. When the dielectric anisotropy of the liquid crystal material is positive, the long axis of the liquid crystal molecule is parallel to the electric field, and when it is negative, it is perpendicular to the electric field. To be oriented.

Taking the case of FIG. 3 as an example, there is a region between the pair of substrates that is curved so that the lines of electric force are convex upward, which means that the electric field is parallel to the substrates. It shows that it also has other components. Therefore, when an electric field is applied with the above electrode arrangement, the liquid crystal molecules can be aligned in directions other than parallel to the substrate in the substrate according to the above matter. In such a case, alignment failure of the liquid crystal material occurs.

Such a variation in the lines of electric force is a drawback that cannot be ignored when pixels are miniaturized. This is because as the number of electrodes increases due to miniaturization and the distance between the electrodes decreases, a discontinuous electric field is distributed at high density.

As another solution to the above problem, Japanese Patent Laid-Open No. 6-214244 proposes an invention in which the electrodes have a high cell thickness in order to uniformly apply an electric field to the liquid crystal in the cell thickness direction. . However, to make extremely tall electrodes,
The following technical difficulties arise.

First, if the height of the electrode is about the cell thickness, the difference in the electrode thickness in the lateral direction between the apex and the bottom of the electrode tends to become large. Super TF that drives liquid crystal by lateral electric field
In the T method, the difference in electrode thickness, that is, the difference in the distance between the electrodes.
Therefore, since the electric field strengths in the cell thickness direction are different in the same pixel, it becomes difficult to drive the liquid crystal.

Second, if the electrode height is extremely high, the coverage of the layer formed thereon is poor, and if the layer formed above is an electrode, disconnection is likely to occur.

Thirdly, it is technically difficult to reduce the film thickness in the lateral direction and obtain a large taper angle with an extremely high electrode even in the miniaturization of pixels.

In order to solve the above problems in the miniaturization of pixels, there is a demand for an electrode structure which can be formed by a simple method and which does not generate a discontinuous electric field.

Still another problem is that since the liquid crystal driving electrode and the common electrode are metal electrodes made of Al or the like, the aperture ratio is lowered.

In the conventional liquid crystal electro-optical device, a common electrode is formed on a counter substrate, and the common electrode is generally made of a material having a light transmitting property, such as ITO. However, the liquid crystal electro-optical device of the lateral electric field drive system has a liquid crystal drive electrode and a common electrode formed on one of the substrates, and both electrodes use a light-shielding electrode made of Al or the like, which is effective. There is a drawback that the display area is reduced as compared with the conventional liquid crystal electro-optical device, that is, the aperture ratio is reduced.

[0019]

The liquid crystal electro-optical device of the present invention comprises a plurality of electrodes formed on a pair of substrates.
Controls the electric field (transverse electric field) strength in the direction parallel to the substrate,
This is a method of operating a liquid crystal material. However, as in the conventional lateral electric field driving method, the liquid crystal driving and common electrodes are not formed only on one of the substrates as in the conventional lateral electric field driving method, but an electrode is also formed on the other substrate, and when driving the liquid crystal, this electrode is used. Also applies an electric field to solve problems such as nonuniformity of electric field strength, which have been a problem until now.

Furthermore, it is intended to provide a liquid crystal electro-optical device having improved visual characteristics by improving the reduction in aperture ratio due to the use of the light-shielding electrode.

[0021]

In order to solve the above problems, the present invention provides a pair of substrates at least one of which is transparent,
A pair of electrodes for driving a liquid crystal having electrodes formed on both of the substrates and a liquid crystal layer sandwiched between the substrates, the electrodes being capable of forming an electric field including a direction parallel to the substrate surface. Wherein the pair of electrodes have portions arranged substantially parallel to each other, and the liquid crystal electro-optical device is provided with an electric field applying unit that applies an electric field to the liquid crystal layer via the electrodes. In the liquid crystal electro-optical device, the electric field distribution formed between the pair of electrodes on the substrate is controlled by the electric field strength formed between the pair of electrodes on the other substrate.

According to another structure of the present invention, a pair of substrates, at least one of which is transparent, and electrodes formed on both of the substrates,
A liquid crystal layer sandwiched between the substrates, the electrodes,
It includes a pair of electrodes for driving a liquid crystal capable of forming an electric field including a direction parallel to the substrate surface, the pair of electrodes having portions arranged substantially parallel to each other, and applying an electric field to the liquid crystal layer through the electrodes. In a liquid crystal electro-optical device including an electric field applying unit that applies an electric field, an electric field formed between a pair of electrodes on one of the substrates is equal to an electric field formed between a pair of electrodes on the other substrate. The liquid crystal electro-optical device is characterized in that the electric field distribution is made uniform in the cell thickness direction by the interaction of.

According to another structure of the present invention, a pair of substrates, at least one of which is transparent, and electrodes formed on both of the substrates,
A liquid crystal layer sandwiched between the substrates, the electrodes,
It includes a pair of electrodes for driving a liquid crystal capable of forming an electric field including a direction parallel to the substrate surface, the pair of electrodes having portions arranged substantially parallel to each other, and applying an electric field to the liquid crystal layer through the electrodes. A liquid crystal electro-optical device provided with an electric field applying means for applying an electric field in the same direction to the liquid crystal layer at the same time by an electrode between the pair of substrates, thereby providing an electric field distribution between the pair of substrates. It is a liquid crystal electro-optical device characterized by controlling.

According to another structure of the present invention, a pair of substrates, at least one of which is transparent, and electrodes formed on both of the substrates,
A liquid crystal layer sandwiched between the substrates, the electrodes,
It includes a pair of electrodes for driving a liquid crystal capable of forming an electric field including a direction parallel to the substrate surface, the pair of electrodes having portions arranged substantially parallel to each other, and applying an electric field to the liquid crystal layer through the electrodes. A liquid crystal electro-optical device comprising an electric field applying unit for applying the electric field, wherein the pair of electrodes are arranged at positions facing each other on both substrates.

An example of a configuration utilizing the invention disclosed in this specification is shown in FIGS. 1 and 2. FIG. 1 is a schematic diagram of a pixel portion of an active matrix liquid crystal electro-optical device that uses a nematic liquid crystal, drives the liquid crystal material in a lateral electric field, and uses a poly-Si TFT as the driving element. This is the case when the device is viewed from above (from the direction perpendicular to the substrate surface), and since some wirings are arranged so as to overlap, only the wirings on the upper substrate can be seen. Further, FIG. 2 shows a cross section in the AA 'direction in FIG.

In the structure shown in FIGS. 1 and 2, on the first substrate (101), a base SiO ₂ film (103), a gate electrode (105), a common electrode (107) and a gate insulating film are extended. A layer (109), a switching element (111), a source electrode (113), a liquid crystal driving electrode (115), a protective film (117), and an alignment film (119).

On the other hand, the second substrate (102) has a base Si layer.
O ₂ film (104), gate electrode (106), common electrode (108), layer (11 extending from the gate insulating film
0), switching element (112), source electrode (11
4), a liquid crystal driving electrode (116), a protective film (118),
An alignment film (120) is formed. Also, (121)
Is a liquid crystal layer.

The liquid crystal driving electrode (115) and the common electrode (107), or the liquid crystal driving electrode (116) and the common electrode (108) are arranged substantially parallel to each other.

Here, the gate electrodes (105), (1
06) has a function as a gate wiring (scanning line), and the source electrodes (113) and (114) have a function also as source wiring (signal lines). In addition, the common electrode (10
7) and (108) correspond to the common electrode. further,
When the alignment state of the liquid crystal layer (121) is described, liquid crystal molecules are also shown.

In the case of the liquid crystal electro-optical device, an electric field is first applied between the liquid crystal driving electrode (115) and the common electrode (107) for driving the liquid crystal material formed on the first substrate (101). The liquid crystal molecules in the liquid crystal layer (121) are switched (alignment state is changed) in a plane parallel to the substrate by the electric field.

However, when an electric field is applied only between the electrodes on the first substrate (101), the electric field strength decreases toward the second substrate (102), so that the liquid crystal material (121).
The control of the orientation direction of is insufficient.

Therefore, the liquid crystal driving electrode (116) and the common electrode (107) are also provided on the second substrate (102). At that time, in the first substrate and the second substrate,
The electrodes are arranged at positions facing each other.

That is, the liquid crystal driving electrode (116) of the second substrate (102) is provided on the liquid crystal driving electrode (115) of the first substrate (101), and the first substrate (101) is also provided.
On the common electrode (107) of the second substrate (102)
Of the second substrate (102) so that the common electrodes (108) of each are arranged respectively.
An electric field is also applied between the common electrodes (108).

Then, the electric field distribution between the electrodes (115) and (107) on the first substrate (101) is changed by the electric field between the electrodes (116) and (108) on the second substrate (102). The force lines are deformed and can be controlled to indicate various states. In particular, the electric field strength between the two electrodes (115), (107) on the first substrate (101),
The two electrodes (116) on the second substrate (102),
When the electric field strength between (108) is the same, the electric field strength distribution becomes constant at any place between the upper and lower substrates (101), (102).

The first and second substrates (101),
For (102), a material having a light-transmitting property and having a certain strength against an external force, for example, an inorganic material such as glass or quartz is used. A non-alkali glass or quartz glass is used for a substrate on which a TFT or the like is formed (hereinafter referred to as a TFT substrate). In addition, for the purpose of reducing the weight of the liquid crystal electro-optical device, a film having a low birefringence, such as PES, is used.
(Polyethylene sulfate) or the like can also be used.

Further, the driving method of the liquid crystal material (121) may be a multiplex method or an active matrix method.

In the multiplex system, the first substrate (1
The liquid crystal driving electrode (115) and the common electrode (107) need only be formed on top of the above (01), but in the case of the active matrix system, the switching element (11) is also added.
As 1) and (112), a non-linear element such as a thin film transistor (TFT) or a diode is formed for each pixel.
In the case of a thin film transistor, the drain electrode is connected to the liquid crystal driving electrodes (115) and (116), and the common electrode is separately provided as the common electrodes (107) and (108).

As the TFT, a transistor using amorphous silicon or poly (polycrystalline) silicon for the active layer can be used. In the case of the active matrix system, the structure of the drive element may be a known structure such as a stagger type or an inverted stagger type. When a transistor including polysilicon is used, a peripheral driver circuit for driving a liquid crystal material can be formed over the substrate over which the TFT is manufactured. The peripheral driver circuit can be manufactured by the same process as that for manufacturing a TFT. This peripheral drive circuit is formed by a complementary element in which n-ch and p-ch transistors are combined.

The switching elements (111), (1
For 12)), it is desirable to use a poly-Si type TFT. In particular, when poly-Si is used for the TFT active layer, the mobility of the active layer is higher than when a-Si is used for the TFT active layer, and the same characteristics as a-Si can be obtained in a smaller element region. Therefore, it is possible to miniaturize each element, and eventually to increase the aperture ratio. In addition, when a lateral electric field is applied, a poly-Si having a large carrier mobility is used for the TFT.
Higher-speed response can be realized when used for the active layer. Furthermore, when poly-Si is used, it becomes possible to form a peripheral drive circuit for driving the liquid crystal material on the substrate, which contributes to a reduction in device manufacturing process, an improvement in yield, and a decrease in device cost.

As the device electrode, a gate electrode (10
5), the source electrode (113) is made of a metal such as Al, Ti, or Ta, a metal-containing material, a metal oxide, or S.
A material containing phosphorus, boron, etc. in i, Si, carbon, a material containing carbon, etc. can be used. In order to increase the pixel density, both gate and source electrodes (10
Since the signal delays in 5) and (113) cannot be ignored, it is desirable to use a material having a low volume resistivity.
In addition, the liquid crystal driving electrode (115) and the common electrode (10
For 7), ITO or the like can be used in addition to the above various materials. In particular, the use of a light-transmitting material such as ITO can improve the pixel aperture ratio.

The cross section of the electrode has a rectangular shape, a trapezoidal shape, or a curved cross section. In the case of a rectangular or trapezoidal cross section, a well-known patterning / etching method may be used. As a method of forming a curved cross section, anisotropic plasma etching, isotropic plasma etching, etc. are combined to form a smooth or curved electrode cross section. May be included. As a method for forming a cross section having a smooth surface or a curved surface shown in this specification, either a dry process or a wet process can be used. The above method is an example of a method for producing an electrode having a gentle curved section, and the method for producing an electrode having a gentle curved section is not limited to these methods.

Further, it is possible to use silicon oxide (SiO ₂ ) or silicon nitride (SiN) as each interlayer insulating film (109) and TFT protective film (117). Furthermore, it is also possible to use an acrylic resin or an organic resin made of polyimide or the like.

FIG. 8 shows a schematic cross-sectional view of a liquid crystal electro-optical device in which an organic resin is used as a TFT protective film and the other structures are the same as those described above. In particular, when an organic resin is used as the TFT protective film, it can be used as a flattening film (801) for smoothing the substrate surface. Since the liquid crystal electro-optical device of the present invention utilizes the birefringence of the liquid crystal material, unevenness in the distance between the pair of substrates causes uneven color. Therefore, it is important that the substrate interval is constant over the entire device, and the planarization process is an important process for improving the yield of device manufacturing.

Next, for the second substrate (102), it is possible to use the same material as that for the first substrate (101). The liquid crystal material (12) is also formed on the second substrate (102).
An electrode for driving 1) is formed. As the electrode material at this time, the element (111) on the first substrate (101),
Each electrode (105), (107), (113), (11
The material used to form 5) can be used.

The electrodes are arranged so that the driving electrodes (115) and the common electrodes (107) of the first substrate (101) are alternately arranged at equal intervals.

Also, both substrates (101), (102)
The elements (111), (112) and the electrodes (1)
05), (106), (107), (108), (11
3), (114), (115), and (116), in order to maximize the effective display area, that is, the aperture ratio, for example, as shown in FIG.
1), gates (105), (106) and sources (113), (114) and liquid crystal driving electrodes (115), (116) and a common electrode (107) on (102),
The wirings of (108) may be arranged so as to overlap each other. By doing so, it is possible to obtain the same aperture ratio as in the case where the gate and source wirings are formed on one of the substrates as in the conventional liquid crystal electro-optical device.

Further, on the first substrate (101), the second substrate (102), or both substrates, in order to improve the contrast, a portion not related to the display is shielded from light, so that metal such as Cr or black is used. A black matrix is formed by a resin material in which the pigment is dispersed (not shown). Further, in the case of color display, R (red), G (green), B (blue) or C (cyan), M (magenta), Y (yellow) color filters are formed at positions corresponding to each pixel. . As the arrangement of each color of the color filter, a stripe arrangement or a delta arrangement can be used.

Then, the first substrate (101) and the second substrate (102) were subjected to orientation treatment. The alignment treatment is performed so that the liquid crystal molecules are aligned parallel to the substrate and uniaxially. As the alignment treatment, the substrate surface is directly applied, or after the films (orientation films) (119) and (120) made of an organic resin such as nylon or polyimide are applied, the resin surface is applied.
A rubbing process of rubbing in one direction is effective. It is also possible to eliminate the process of forming the alignment film by directly subjecting the surface of the TFT protective film (planarization film (801)) made of the organic resin to the alignment treatment such as rubbing.

5 and 6, the rubbing direction (50
2) and (503) are shown. The rubbing direction depends on the liquid crystal material (121) used, and the first substrate (101) side is not parallel to the electric field when the material has positive dielectric anisotropy, and preferably has a direction of 45 ° with the electric field. And
Furthermore, in the case of a material having a negative dielectric anisotropy, the direction is not perpendicular to the electric field, preferably 45 ° with the electric field. The rubbing process on the second substrate (102) side is performed in parallel or anti-parallel to the rubbing direction of the first substrate (101).

The pair of substrates (101) and (102) produced in this manner are stacked at a constant interval to form a liquid crystal cell. The pair of substrates (10
A sealant (not shown) as an adhesive is formed in a desired pattern on either one of 1) and (102). As the sealant, a thermosetting type resin material, an ultraviolet ray curing type resin material or the like is used. As the resin material, an epoxy-based material, a urethane acrylate-based material, or the like can be used. Further, spacers (not shown) are sprayed on the other substrate to keep the distance between the pair of substrates constant throughout the cell.

After the sealing agent is cured, the liquid crystal material (121) is injected into the liquid crystal cell by a vacuum injection method or the like. The liquid crystal layer (121) may be formed in advance on one of the substrates before forming the sealant, and then the sealant may be formed and the other substrate may be superposed.

Examples of the liquid crystal material that can be used in the present invention include materials exhibiting nematic, cholesteric, and smectic properties, and nematic materials are particularly preferably used. Further, among the nematic liquid crystals, those having a positive or negative dielectric anisotropy depending on the driving method are appropriately selected and used. Furthermore, a wider viewing angle can be obtained by using one having a small refractive index anisotropy.

Further, the alignment state of the liquid crystal material of the liquid crystal electro-optical device of the present invention is schematically shown in FIGS. Here, as an example, the case where a material having a negative dielectric anisotropy is used is shown. FIG. 5 shows an alignment state when no electric field is applied, and FIG. 6 shows an alignment state when an electric field is applied. In this figure, as a schematic diagram, the electrodes (107), (115), as constituents on the pair of substrates,
(108), (116), and alignment films (119), (1
20) is shown, and other elements, wirings, etc. are omitted.

Since the liquid crystal electro-optical device uses the birefringence of the liquid crystal material for display, a pair of polarizing plates (50
1) and (502) are arranged so that their optical axes (505) and (506) are orthogonal to each other, and a liquid crystal cell is sandwiched between the pair of polarizing plates. At this time, the alignment direction of the liquid crystal material (121) is parallel to the optical axis of the analyzer, that is, the polarizing plate closer to the light source.

In the liquid crystal electro-optical device manufactured in this manner, the liquid crystal material (121) is aligned in the rubbing direction with the long axis parallel to the substrate as shown in FIG. 5 when no electric field is applied. It is uniaxially oriented parallel to (503) and (504).

Next, the electrodes (107), (115), (1
When an electric field is applied to (08) and (116), as shown in FIG. 6, liquid crystal molecules (12
In 2), the direction parallel to the rubbing directions (503) and (504) is maintained, and the optical axis of the liquid crystal molecule (123) near the center of the liquid crystal layer where the alignment control force is weak is changed by the electric field. When a liquid crystal material having a positive dielectric anisotropy is used, liquid crystal molecules (123)
The major axis of the liquid crystal molecules is oriented parallel to the electric field direction, and when the dielectric anisotropy is negative, the major axis (123) of the liquid crystal molecules is perpendicular to the electric field direction as shown in FIG. It will be like this.

Therefore, with respect to light transmitted through the liquid crystal electro-optical device, the orientation of the liquid crystal material (121) is parallel to the optical axis (505) of the analyzer (501) in the cell when no electric field is applied, so that the incident light is The polarizer (502) cannot be transmitted, and the amount of transmitted light at this time becomes zero. On the other hand, when an electric field is applied, the direction of the optical axis of the liquid crystal material (121) changes, so that the incident light becomes elliptically polarized light and passes through the polarizer (502).

When displaying, a selection signal (scanning signal) is first applied to the gate electrode (105) of the first substrate at an arbitrary period.
Is applied and the video data applied to the source electrode (113) is applied to the liquid crystal driving electrode (115) because the switching element (111) becomes conductive during the selection period. On the other hand, the common electrode (107) is grounded or an arbitrary waveform is applied.

Then, there is a component parallel to the substrate between the liquid crystal driving electrode (115) and the common electrode (107) and perpendicular to the longitudinal direction of the liquid crystal driving electrode (115) and the common electrode (107). An electric field is formed, and the liquid crystal molecules (121) are caused by the electric field to form the substrates (101) and (102).
Switching occurs in a plane parallel to (the orientation state changes), and the image data is written in the pixel.

After the end of the selection period, the switching element (11
1) is in a non-conducting state. Liquid crystal driving electrode (115)-
The applied electric field is held between the common electrodes (107), and the written video data is saved.

Hereinafter, scanning signals are sequentially applied to the gate electrode (105) on the first substrate (101), and the substrate (10
1) Write video data to the whole.

However, when an electric field is applied only to the first substrate (101), the electric field strength increases near the electrodes of the first substrate (101), but the electric field strength decreases as it approaches the second substrate (102). Resulting in. In addition, there are many electric fields having components other than parallel to the substrate. Therefore, the liquid crystal drive electrode (11) provided on the second substrate (102).
6), with respect to the common electrode (108), the first substrate (1
01) liquid crystal driving electrode (115) -common electrode (10)
7) An electric field is applied to control the distribution state of the electric field formed between the two.

Regarding the method of applying the electric field, the electric field is applied to the first substrate (101) and the second substrate (102) at the same time. Furthermore, the direction of the electric field is the upper and lower substrates (101),
At (102), the directions are the same.

Therefore, the same video data is written between the electrodes on the second substrate (102) at the same timing as the video data is written between the electrodes on the first substrate (101).
As a result, an electric field having a component parallel to the substrate is formed in each portion between the pair of substrates (101) and (102), and the lines of electric force are parallel within the pixel.

Although the two polarizing plates (501) are used in the above, the pair of substrates (101), (1)
If a reflecting plate made of a metal or the like is formed on either one of 02), a liquid crystal electro-optical device can be manufactured using only one polarizing plate, and a bright display can be realized. Further, the metallic reflection plate can also serve as an electrode of a pixel or the like.

[0066]

When the liquid crystal electro-optical device according to the present specification is constructed, the electric flux density in the cell in the cell thickness direction becomes uniform as compared with the conventional lateral electric field driving type liquid crystal electro-optical device. As a result, almost all liquid crystal molecules in the cell thickness direction similarly change their orientation vectors when an electric field is applied. As a result, the rising of the display and the response characteristics are improved.

The continuity of this electric field is apparent from the aspect of the lines of electric force around the electrodes when a voltage is applied to the electrodes. Hereinafter, the mode of the lines of electric force around the electrodes will be described with reference to FIG.

When an electric field is applied to the inside of the cell by the above driving method, as shown in FIG. 4, it is formed when an electric field is applied only between the electrodes (107) and (115) on one substrate (101). The generated electric force lines (306) (curves represented by dotted lines in FIG. 4) are the electrodes (116), (1
08), the electric field is deformed in the direction of the arrow (307) in the figure, and the electric line of force (306) is effectively represented by the solid line in the figure. Therefore, the distribution of the lines of electric force of the liquid crystal electro-optical device of the present invention is more uniform than in the case where the electrodes are formed only on one of the substrates.

The trapezoidal electrode section has been described above as an example, but the present invention is not limited to this, and the same effect can be obtained even if the electrode section uses a circular or elliptic curvature. Further, the same effect can be obtained not only when the cross-sectional shape is a regular semicircle but also when an arc is formed. Further, the edge cross section of the electrode may have a curved surface such as an arc. Of course, an electrode having a cross section having a polygonal shape with gentle boundary changes may be used.

Furthermore, a film formed on a thin film such as an electrode having a gentle curved cross section has good coverage because of the roundness of the thin film. Therefore, there is also an effect of preventing contamination of impurities, disconnection, and the like due to poor coverage.

In the present invention, the liquid crystal electro-optical device of the type in which the lateral electric field is applied to the liquid crystal material has been described.
Without being limited to this, for example, when used in a liquid crystal electro-optical device of a method of applying a vertical electric field such as a conventional TN method,
Disturbance of the electric field in the cell can be reduced, and an electro-optical device with good coverage can be manufactured. Embodiments of the present invention will be described below with reference to the drawings.

[0072]

【Example】

[Embodiment 1] In this embodiment, a monolithic active matrix circuit in which a peripheral drive circuit is also formed on a substrate is used. This production process will be described with reference to FIG. FIG. 7 is a schematic view of the periphery of the peripheral drive circuit. The left side shows the steps of manufacturing the TFT of the drive circuit, and the right side shows the steps of manufacturing TFT of the active matrix circuit. Note that this step is a low temperature polysilicon process.

First, a base oxide film (103) was formed on Corning # 1737 as the first insulating substrate (101). As a method of forming this silicon oxide film, a sputtering method in an oxygen atmosphere or a plasma CVD method may be used.

After that, an amorphous silicon film of 300 to 1500 is formed by a plasma CVD method or an LPCVD method.
Å, preferably 500 to 1000Å. Then, thermal annealing was performed at a temperature of 500 ° C. or higher, preferably 500 to 600 ° C. to crystallize the silicon film or enhance the crystallinity. After crystallization by thermal annealing, optical (laser etc.) annealing may be performed to further enhance crystallization. In addition, when crystallizing by thermal annealing, Japanese Patent Laid-Open Nos. 6-244103 and 6-244104
As described in (1), an element (catalyst element) that promotes crystallization of silicon such as nickel may be added.

Next, the silicon film is etched to form islands, and the active layers (701) (for P-channel TFTs) of the TFTs of the drive circuit, (702) (N-channel TFTs).
Active layer (703) of the TFT (pixel TFT) of the matrix circuit. Further, a gate insulating film (704) of silicon oxide having a thickness of 500 to 2000 Å was formed by a sputtering method in an oxygen atmosphere. A plasma CVD method may be used as a method for forming the gate insulating film. When the silicon oxide film is formed by the plasma CVD method,
It was preferable to use dinitrogen monoxide (N ₂ O) or oxygen (O ₂ ) and monosilane (SiH ₄ ) as the source gas.

After that, aluminum having a thickness of 2000 to 6000Å was formed on the entire surface of the substrate by the sputtering method. Here, aluminum may contain silicon, scandium, palladium, or the like in order to prevent hillocks from being generated by a subsequent thermal process. Then, isotropic plasma etching was performed to form gate electrodes (705), (706), (707) and a common electrode (708) (common electrode) (FIG. 7A). At this time, the discharge gas voltage was appropriately set, and the electrodes had curved surfaces. After that, by an ion doping method, all the island-shaped active layers are self-aligned using the gate electrode as a mask,
Phosphorus is injected using phosphine (PH ₃ ) as a doping gas. The dose amount is 1 × 10 ^{12 to} 5 × 10 ¹³ atoms /
cm ² As a result, a weak N-type region (709),
(710) and (711) were formed. (Fig. 7 (B
))

Next, a photoresist mask (712) covering the P-channel active layer and the active layer (7) of the pixel TFT.
13), the gate electrode (70
A photoresist mask (713) is formed so as to cover a portion 3 μm away from the end of 8). Then, phosphorus is injected again using phosphine as a doping gas by the ion doping method. Dose amount is 1 × 10 ^{14 to} 5 × 10 ¹⁵
Atom / cm2. As a result, strong N-type regions (source and drain) (714) and (715) are formed. The region (716) covered with the photoresist (713) on the pixel TFT remains weak N-type because phosphorus is not implanted in this doping. (Fig. 7 (C
))

Next, the active layer of the N-channel TFT (70
2) and (703) are photoresist masks (717)
Then, boron is implanted into the island region (701) by an ion doping method using diborane (B ₂ H ₆ ) as a doping gas. The dose amount is 5 × 10 ¹⁴ to 8 × 10 ^15.
Atom / cm ² . In this doping, since the dose amount of boron exceeds the dose amount of phosphorus in FIG. 7C,
The previously formed weak N-type region (708) is inverted into a strong P-type region (718). By the above doping,
Strong N-type region (source / drain) (714), (71
5), strong P-type region (source / drain) (718),
A weak N-type region (low concentration impurity region) (716) is formed. (FIG. 7 (D))

After that, thermal annealing was performed at 450 to 850 ° C. for 0.5 to 3 hours to recover the damage caused by the doping, activate the doping impurities, and recover the crystallinity of silicon. After that, a silicon oxide film having a thickness of 3000 to 6000Å was formed on the entire surface as an interlayer insulator (719) by a plasma CVD method. This may be a silicon nitride film or a multilayer film of a silicon oxide film and a silicon nitride film. Then, the interlayer insulating film (719) was etched by wet etching or dry etching to form contact holes in the source / drain.

Then, a thickness of 2000 is obtained by the sputtering method.
An aluminum film of 6000 Å or a multilayer film of titanium and aluminum is formed. This was subjected to isotropic plasma etching using the resist as a mask. At this time, the discharge gas voltage is appropriately set, the electrodes have curved surfaces, and electrodes / wirings (720), (721), (722) of the peripheral circuit are provided.
And electrode / wiring of pixel TFT (723), (724)
Was formed. The electrode (724) is a liquid crystal driving electrode (11
The wiring pattern also serves as 5). Further, a silicon nitride film (725) having a thickness of 1000 to 3000 Å was formed as an interlayer film by the plasma CVD method. (FIG. 7
(E))

Further, a TFT and a common electrode were formed on the second substrate (102) similarly to the first substrate (101). The patterns of the elements and wiring electrodes on the first substrate (101) and the second substrate (102) are, as shown in FIG. 2, liquid crystal driving electrodes (115) and (116) and a common electrode (107). , (108) have a constant interval, and the gate electrodes (105), (106),
Source electrodes (113), (114) and TFT (11
As for 1) and (112), they were arranged at appropriate positions so that the aperture ratio of the pixel was maximized. Further, the wiring patterns of the first substrate (101) and the second substrate (102) have a relationship in which the right and left are just inverted.

On the first substrate (101), the second substrate (102), or both substrates, a metal such as Cr or black is used to shield the portion not related to display for improving contrast. A black matrix was formed from a resin material in which the pigment was dispersed.

After that, an alignment film (11) made of polyimide was formed on the first substrate (101) and the second substrate (102).
9) and (120) were formed. As the alignment film, polyimide was formed by a known spin coating method or DIP method. Next, the surface of the alignment film was rubbed.

The rubbing directions (503) and (504) differ depending on the liquid crystal material (121) used, and the direction (503) toward the first substrate (101) is a material having a positive dielectric anisotropy. The direction is non-parallel to the electric field direction and forms an angle of 45 ° or closer to the electric field direction with respect to the electric field direction. Furthermore, in the case of a material having a negative dielectric anisotropy, it is 45 ° in a direction that is non-perpendicular to the electric field and perpendicular to the electric field.
Alternatively, the direction is closer to the direction perpendicular to the electric field. The rubbing process (504) on the second substrate (102) side is performed in parallel or anti-parallel to the rubbing direction of the first substrate (101).

The first substrate (1 thus formed)
01) and the second substrate (102) were overlaid to form a liquid crystal panel. The pair of substrates (101), (102)
A spherical spacer having a diameter of 3 μm was sandwiched between the substrates so that the substrate spacing was uniform over the entire panel surface. Further, the pair of substrates (101) and (102) were sealed with an epoxy adhesive in order to bond and fix them. The seal pattern was made to surround the pixel region and the peripheral drive circuit region. After that, the pair of substrates (101) is formed into a predetermined shape,
After cutting (102), liquid crystal material (121) is provided between the substrates.
Was injected.

Next, two polarizing plates (501) and (502) were attached to the outside of the substrate. Regarding the arrangement of the polarizing plates, a pair of polarizing plates are arranged so that their optical axes (505) and (506) are orthogonal to each other, and the optical axis of either one of the polarizing plates, for example, the optical axis (505 of the polarizing plate (501). ) To the rubbing direction (5
It was parallel to 03).

The optical characteristics of this liquid crystal electro-optical device were measured. As a result, a good display with less variation in rising characteristics was obtained as compared with a liquid crystal display having a conventional electrode shape.

According to the structure of this embodiment, since the driving circuit is formed on the same substrate as the pixel portion TFT, there is an advantage that the manufacturing cost can be reduced.

Example 2 FIG. 8 shows a sectional view of the liquid crystal electro-optical device of this example. In this embodiment, the first substrate (1
01) and the second substrate (102), the pixel TFT and the peripheral drive circuit were formed in the same manner as in Example 1. Where T
After forming the FT protective film, the alignment film is not directly formed, but the flattening film (801) is formed, and then the alignment film (119),
(120) was formed.

The flattening film (801) is made of acrylic resin or polyimide resin, and acrylic resin is used here. As the acrylic resin, a two-component thermosetting type resin was used. The flattening film was formed by a known spin coating method or the like, and the film thickness was set to 1 to 2 μm, here 1.5 μm at maximum. As a result, the step difference on the substrate surface caused by forming the element such as the TFT was significantly reduced.

Thereafter, the alignment film (11
9) and (120) were formed, and rubbing treatment was performed. The rubbing direction is the same as in Example 1, and the pair of substrates (10
The parallel or anti-parallel relationship is established between 1) and (102).

The first substrate (1
01) and the second substrate (102) were cell-assembled as a liquid crystal cell in the same manner as in Example 1, and the liquid crystal material (121) was sandwiched between the pair of substrates (101) and (102). Further, a polarizing plate (501) was arranged in the same manner as in Example 1.

In the liquid crystal electro-optical device described above, a good device could be produced with a good yield without occurrence of color unevenness due to uneven cell thickness.

In this embodiment, the flattening film (801) is formed after the TFT protective film is formed. However, the flattening film (801) is used instead of the protective film (725) to form a TFT. The protective film may have a function of simultaneously flattening the surface of the substrate. In addition, a flattening film (80
1) Instead of forming alignment films (119) and (120) after formation and performing alignment treatment such as rubbing, a flattening film (80)
1) The top may be rubbed directly. By doing so, it is not necessary to form the TFT protective film and the alignment films (119) and (120), and the number of manufacturing steps can be significantly reduced.

[Embodiment 3] In this embodiment, similarly to Embodiments 1 and 2, the peripheral drive circuit is an active matrix circuit formed on the substrate. FIG. 9 shows a process of manufacturing the active matrix substrate of this example. In this embodiment,
As the first substrate (101) and the second substrate (102), pixel TFTs and peripheral drive circuits were formed basically in the same manner as in Example 1. However, ITO was used for the liquid crystal driving electrode (901) and the common electrode (902) as pixel electrodes.

The steps of manufacturing each element and each electrode on the substrate are the same as those in Example 1 up to the step of forming a layer made of aluminum or the like for the gate electrode, and the gate electrode is formed by isotropic plasma etching. (705), (70
After forming 6) and (707), ITO is formed by a known method.
Was deposited to 1000 to 3000Å, and the common electrode (902) was formed by isotropic plasma etching (Fig. 9).
(A)).

Thereafter, the same steps as in Example 1 are performed until a layer made of aluminum or the like for wiring of the peripheral drive circuit is formed, and the electrode / wiring (720) of the peripheral drive circuit is formed by isotropic plasma etching. (721), (722)
After forming the electrodes / wirings (723) and (724) of the pixel TFT, 1000 to 300 ITO is formed by a known method.
A 0Å film was formed, and a liquid crystal driving electrode (901) was formed by isotropic plasma etching. This electrode is connected to the drain electrode (724) of the pixel TFT (FIG. 9 (E)).

Next, the silicon nitride film (722) of Example 1 was formed as a TFT protective film. After that, an organic resin film (801) as in Example 2 may be formed as a flattening film.

On the other hand, each element, each electrode, etc. were formed on the second substrate (102) in the same process as above. The relationship between the wiring patterns on the first substrate (101) and the second substrate (102) is the same as in the first embodiment.

The pair of substrates (101) and (102) on which the elements / electrodes etc. were formed in this manner were subjected to orientation treatment, seal printing, substrate superposition / adhesion, liquid crystal injection, by the method shown in Example 1. A liquid crystal electro-optical device was manufactured through a series of liquid crystal panel manufacturing steps such as installation of a polarizing plate.

Since the liquid crystal electro-optical device uses the translucent ITO as the pixel electrode, it has a high pixel aperture ratio and is a bright display that can effectively use the light from the light source.

[Embodiment 4] This embodiment shows an example in which the liquid crystal electro-optical devices manufactured in Embodiments 1, 2 and 3 are dot-sequentially driven for display.

In the case of the present embodiment, the video signals necessary for forming one screen were simultaneously applied to the pair of substrates. As a result, one frame is formed, and thereafter, this is repeated.

In one section, the scanning signal is sequentially applied to the gate line of one substrate, and the video data sampled by the sampling pulse is sequentially held in the source line within the period in which one gate line is selected. Immediately after that, video data is written in each pixel. The video data written in the pixel is held for one section by the liquid crystal and the capacitive component. During this period, the same image as the display image formed on the other substrate is formed on the other substrate, so that the same image data is applied to the same pixel.

In this embodiment, the frame frequency is 60 Hz.
And Therefore, the frequency of one section is 120 Hz. By doing so, even if the output of the video data is switched between the upper and lower substrates as in the present embodiment, it cannot be recognized with the naked eye, and it seems as if one screen is formed and displayed. It was

In this embodiment, the dot-sequential driving is described as an example, but the line-sequential driving may be performed.

[0107]

As described above, according to the present invention, the liquid crystal electro-optical device has better rising characteristics of liquid crystal than the conventional lateral electric field driving type liquid crystal electro-optical device and can be obtained by a simple process. Further, the present invention can cope with miniaturization of the pixel portion.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating an outline of a pixel region of a liquid crystal electro-optical device according to a first exemplary embodiment.

FIG. 2 is a diagram showing an outline of a cross section of the liquid crystal electro-optical device in Example 1.

FIG. 3 is a diagram showing lines of electric force when an electric field is applied between electrodes in a conventional liquid crystal electro-optical device.

FIG. 4 is a diagram showing lines of electric force when an electric field is applied to the electrodes in the liquid crystal electro-optical device according to the first embodiment.

5A and 5B are diagrams showing an outline of alignment of liquid crystals in the liquid crystal electro-optical device in Example 1 when no electric field is applied.

6A and 6B are diagrams showing an outline of alignment of liquid crystal when an electric field is applied to the liquid crystal electro-optical device in Example 1. FIG.

FIG. 7 is a diagram showing an outline of a cross section of the liquid crystal electro-optical device in Example 1.

FIG. 8 is a diagram showing an outline of a cross section of a liquid crystal electro-optical device in Example 2.

FIG. 9 is a diagram schematically showing a cross section of a liquid crystal electro-optical device according to a third embodiment.

[Explanation of symbols]

101, 102 Substrate 103, 104 Underlayer film 105, 106 Gate electrode 107, 108 Common electrode 109, 110 Gate insulating film 111, 112 Switching element 113, 114 Source electrode 115, 116 Liquid crystal driving electrode 117, 118 Protective film 119, 120 Alignment film 121 Liquid crystal layer (liquid crystal molecule) 122, 123 Liquid crystal molecule 301, 303 Substrate 302, 305 Electrode 304, 306 Electric force line 307 Direction of deformation of electric force line (arrow) 501 Polarizer (analyzer) 502 Polarizer ( Polarizer) 503, 504 Rubbing direction 505, 506 Optical axis of polarizing plate 701, 702, 703 Active layer 704 Gate insulating film (silicon oxide) 705, 706, 707 Gate line 708, 902 Common electrode 709, 710, 711 Weak N-type region 712, 13 photoresist masks 714, 715 strong N-type regions (source / drain) 716 low concentration impurity regions 717 photoresist mask 718 strong P-type regions (source / drain) 719 interlayer insulating films 720-724, 901 peripheral drive circuits, Pixel TFT electrode / wiring 725 Silicon nitride film 801 Flattening film

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Satoshi Teramoto 398 Hase, Atsugi City, Kanagawa Prefecture Inside Semiconductor Energy Research Institute Co., Ltd.

Claims (8)

[Claims] 1. A pair of substrates, at least one of which is transparent, an electrode formed on both of the substrates, and a liquid crystal layer sandwiched between the substrates, wherein the electrodes are parallel to a substrate surface. A pair of electrodes for driving a liquid crystal capable of forming an electric field including a direction, the pair of electrodes having portions arranged substantially parallel to each other, and an electric field applying means for applying an electric field to the liquid crystal layer via the electrodes. A liquid crystal electro-optical device comprising: an electric field formed between a pair of electrodes on one of the substrates, the electric field distribution being controlled by an electric field intensity formed between a pair of electrodes on the other substrate. And a liquid crystal electro-optical device. 2. A pair of substrates, at least one of which is transparent, an electrode formed on both of the substrates, and a liquid crystal layer sandwiched between the substrates, wherein the electrodes are parallel to the substrate surface. A pair of electrodes for driving a liquid crystal capable of forming an electric field including a direction, the pair of electrodes having portions arranged substantially parallel to each other, and an electric field applying means for applying an electric field to the liquid crystal layer via the electrodes. In a liquid crystal electro-optical device comprising: an electric field formed between a pair of electrodes on one of the substrates, due to an interaction with an electric field formed between a pair of electrodes on the other substrate, A liquid crystal electro-optical device having a uniform electric field distribution in the cell thickness direction. 3. A pair of substrates, at least one of which is transparent, an electrode formed on both of the substrates, and a liquid crystal layer sandwiched between the substrates, wherein the electrodes are parallel to the substrate surface. A pair of electrodes for driving a liquid crystal capable of forming an electric field including a direction, the pair of electrodes having portions arranged substantially parallel to each other, and an electric field applying means for applying an electric field to the liquid crystal layer via the electrodes. A liquid crystal electro-optical device comprising: a pair of substrates, wherein an electrode between the pair of substrates simultaneously applies an electric field in the same direction to the liquid crystal layer to control an electric field distribution between the pair of substrates. Characteristic liquid crystal electro-optical device. 4. A pair of substrates, at least one of which is transparent, an electrode formed on both of the substrates, and a liquid crystal layer sandwiched between the substrates, wherein the electrodes are parallel to the substrate surface. A pair of electrodes for driving a liquid crystal capable of forming an electric field including a direction, the pair of electrodes having portions arranged substantially parallel to each other, and an electric field applying means for applying an electric field to the liquid crystal layer via the electrodes. The liquid crystal electro-optical device according to claim 1, wherein the pair of electrodes are arranged at positions facing each other on both substrates. 5. The liquid crystal electro-optical device according to claim 1, wherein at least one electrode has a light-transmitting property. 6. The liquid crystal electro-optical device according to claim 1, wherein the electrode has a curved cross section. 7. The liquid crystal electro-optical device according to claim 1, wherein a non-linear element is connected to the electrode. 8. The liquid crystal electro-optical device according to claim 1, wherein a peripheral drive circuit is formed on one or both of the substrates.